Many A/V receivers out there have up-conversion... but I'm not sure that you understand what that term means. Up-conversion takes a composite or s-video signal and converts it to better interfaces like component. Usually a composite signal is up-converted to s-video and component, and s-video is upconverted to component.

I think where you may be confused is that you talk about "... upconvert the standard cable company signal to something better ..." Note that upconversion will not make your picture look better, it simply reduces the number of cables you need to run, and allows for not having to change the source at the display.

I could be off, but making this guess based on your comment of upconverting the "cable company signal".